1. Field of the Invention
The present invention relates to a dental amalgam alloy containing selenium.
2. Statement of the Prior Art
In using the dental amalgam, the alloy powder composed mainly of silver, tin and copper is amalgamated with mercury, and the resulting amalgam is filled in an oral cavity for setting or curing therein.
The high-copper type amalgam alloys including the dispersion-enhanced type amalgam alloys are used as the amalgam alloys in which no crystallization of the Sn.sub.7-8 Hg(.gamma..sub.2) phase takes place. These alloys have their copper content increased whereby the crystallization of a Cu.sub.3 Sn(.epsilon.) or Cu.sub.6 Sn.sub.5 (.eta.) phase is effected without crystallizing the Sn.sub.7-8 Hg(.gamma..sub.2) phases, resulting in improvements in their mechanical properties. Such improvements give weight to the mechanical properties and corrosion resistance of the cured amalgam. However, any close attention is not paid at all to cytotoxicity resulting from mercury eluting from the amalgam filler.
In recent years, amalgam alloys containing selenium have been proposed in Japanese Patent Laid-Open Publication Nos. 57(1982)-155337 and 58(1983)-171540 in view of the fact that selenium has been found to be an element effective for eliminating cytotoxicity ascribed to mercury in amalgam fillers, and the fact that the triturated amalgams are effective for the elimination of cytotoxicity has been read in and ascertained the academic society.
According to one method for making the dental amalgam alloys containing selenium that has been made public, selenium is dissolved and incorporated into the respective constitutional metals of amalgam alloys, silver alloys or copper alloys, when they are dissolved for alloying. According to another method, the constitutional components are coated on the surface of selenium. According to still another method, selenium powders are directly added to and mixed with the amalgam alloys prepared in the ordinary process. It is considered, however, that these methods are not the best, taking into account the toxicity of selenium vapors or oxides expected to be formed due to a low melting point (689.degree. C.) when selenium is dissolved into molten alloys, the ununiform distribution of selenium caused due to its low specific gravity (about 4.2) during mixing.